This invention relates generally to vehicle fuel systems and more particularly to a fuel flow and pressure regulator for a fuel system with a jet pump.
Electric motor fuel pumps have been used to supply the fuel demand for engines in various applications. In some applications, the fuel pump may be disposed within a reservoir within the fuel tank and may draw fuel directly from the reservoir for delivery to the engine. To provide fuel within the reservoir and available for the fuel pump, some of these fuel systems utilize a portion of fuel discharged under pressure from the fuel pump to operate a jet pump which creates a pressure drop adjacent an inlet of the reservoir to draw fuel from the fuel tank into the reservoir.
In prior fuel systems, the flow path providing fuel from the fuel pump to the jet pump is always fully open and therefore, a significant portion of fuel discharged from the fuel pump is always routed through the jet pump. Undesirably, during low voltage conditions, such as when the vehicle is started in cold weather, a lower than normal voltage may be provided to the fuel pump causing the fuel pump to run at a lower than normal speed and thereby discharge fuel at a relatively low flow rate. Thus, a lower flow rate of fuel is available for the engine, and to compound this problem, a portion of the fuel discharged from the fuel pump is routed away from the engine and to the jet pump as previously described. Thus, during low voltage conditions, an undesirably low fuel flow rate may be provided to the vehicle engine. Therefore, there is a need to improve the flow rate of fuel to the engine during low voltage and other conditions in the vehicle wherein the fuel pump has a low output flow rate.
In a fuel system a fuel pressure regulator is provided between the outlet of the fuel pump and an inlet of a jet pump to control the flow of fuel to the jet pump. Desirably, during low voltage conditions in a vehicle, the flow of fuel to the jet pump may be temporarily restricted or terminated to decrease the amount of fuel diverted from the engine and thereby increase the flow rate of fuel to the engine and improve the performance of the engine. The regulator may also function to bypass fuel delivered from the fuel pump in excess of the engine fuel demand to control the pressure of fuel downstream of the fuel pump delivered to the engine.
Objects, features and advantages of this invention include providing a fuel pressure regulator which controls the maximum pressure of fuel delivered to the engine, bypasses excess fuel discharged from the fuel pump, controls the flow of fuel to a jet pump, may restrict or terminate the flow of fuel to a jet pump during low voltage conditions, improves the performance of the engine during low voltage conditions, is reliable, durable, of relatively simple design and economical manufacture and assembly, and has a long, useful service life.